[Dwarf-Discuss] Split Dwarf vs. CU DW_AT_ranges / DW_AT_low_pc placement

[David Blaikie]

On Wed, Mar 10, 2021 at 4:02 PM Cary Coutant <ccoutant at gmail.com> wrote:

> > > So in the end the logical thing to do when encountering a
> > > DW_FORM_rnglistx in a split-unit, in order to support everybody, is
> > > probably to go to the .debug_rnglists.dwo section, if there's one,
> > > disregarding the (inherited) DW_AT_rnglists_base.  If there isn't, then
> > > try the linked file's .debug_rnglists section, using
> > > DW_AT_rnglists_base.  If there isn't, then something is malformed.
>
> Looks reasonable to me. I think we need a new issue to clarify this in
> DWARF 6.
>

Given that DWARFv5 isn't on by default in GCC yet & I think has a few more
things to do - would it be OK if we avoided that complexity if GCC's going
to move its rnglists to .dwo (except for the CU, per the spec) which should
match LLVM's behavior? Either way old GDBs won't handle GCC's DWARFv5 and
new GCCs will produce GDB-compatible DWARFv5.

I've posted an issue to clarify rnglists the way LLVM uses them - but if
preferred, I can amend that to support the fallback described here.
Hopefully we can avoid that variance/complexity for consumers, though.

Jakub: Any thoughts on this?

- Dave
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